Novel synthesis of substituted 4-amino-pyrimidines

ABSTRACT

The present invention is directed to a process for the manufacture of compounds of formula IV wherein R 1  is an amino protecting group, and R 2  is hydrogen or C 1-10  alkyl, comprising a) reacting a compound of formula Ia, wherein M +  is a cation, preferably selected from the group consisting of Li + , Na+, K + , ms, ½ Mg 2+  and ½ Zn 2+ , (formula 1 a ) with an ammonium salt NH 4 X − , wherein X −  is an anion, preferably selected from the group consisting of chloride, bromide, sulfate and acetate, in a solvent to a compound of formula II b) reacting a compound of formula II with a nitrile R 2 —CN in the presence of a base to a compound of formula IV. The present invention is further directed to compounds of formula II and their use for the manufacture of vitamin B 1 .

The present invention relates to the direct transformation of anN-substituted N-(3-amino-2-cyanoallyl)amine (especially ofN-(3-amino-2-cyanoallyl)formamide) to substituted 4-amino-pyrimidines.In particular it relates to a new reaction to2-alkyl-4-amino-5-formylaminomethylpyrimidines (especially to2-methyl-4-amino-5-formylaminomethyl-pyrimidine) by a cyclizationreaction of N-substituted N-(3-amino-2-cyanoallyl)amines (especially ofN-(3-amino-2-cyanoallyl)formamide) and alkylnitriles such asacetonitrile.

Importance of 4-Aminopyrimidines

4-aminopyrimidines and the aminosubstituted derivatives can be found asstructural elements in several antibiotic substances, in herbicides aswell as in vitamin B₁.

Amprolium (sold as CORID®) for example, thiamin analog, competitivelyinhibits the active transport of thiamin. The coccidia are 50 times assensitive to this inhibition as is the host. It can prevent costlycoccidial infection in exposed cattle and treat clinical outbreaks whenthey do occur. By stopping coccidia in the small intestine, CORID®prevents more damaging coccidiosis in the large intestine.

Importance of 4-Amino-5-Aminomethyl-2-Methylpyrimidine

4-amino-5-aminomethyl-2-methylpyrimidine is an important intermediate inthe synthesis of vitamin B₁. Vitamin B₁ (thiamin) is used chiefly in theform of chloride hydrochloride (1) and nitrate.

It is widespread in nature, for example 2.05 mg/100 g wheat germ, 1.3mg/100 g in soybeans. A deficiency in vitamin B₁ in the human being isassociated with the disease beriberi, with imbalances in carbohydratestatus and deleterious effects on nerve functions. A human being needs20-30 μg/kg body weight, which corresponds to 0.3-1.5 mg/d dailyallowance. Since extraction of thiamin from natural sources would not beeconomically profitable, it has to be manufactured by chemicalsynthesis. Industrial production of vitamin B₁ started in 1937 byHoffmann-La Roche in Switzerland and Merck in the United States.Commercially available forms of thiamin are the chloride hydrochlorideand the mononitrate.

4-amino-5-aminomethyl-2-methylpyrimidine is a key-intermediate in thesynthesis of thiamin which contains a thiazole and a pyrimidine ring.One main approach towards the synthesis of thiamin is the pyrimidinesynthesis and subsequent formation of the thiazole ring attached to thepyrimidine moiety from 4-amino-5-aminomethyl-2-methylpyrimidine and3-chloro-5-hydroxypentan-2-one, the 3-mercaptoketone or thecorresponding acetates. Several procedures have been published for thesynthesis of 4-amino-5-aminomethyl-2-methylpyrimidine. The buildingblocks are based on a C2-unit, e.g. acetamidine, and a C1-unit, usuallyfrom CO. Acrylonitrile can be used as C3-unit as a cheap startingmaterial for the synthesis.

STATE OF THE ART

JP 39022009 and JP 39022010 describe the synthesis of2-methyl-4-amino-5-formyl-aminomethylpyrimidine by reacting formamidinehydrochloride with sodium and ethanol to liberate the amidine followedby an addition of 2-(ethoxymethoxymethyl)-3-ethoxy-propionitrile. Thisprocedure is disadvantageous as it necessitates an extra reaction step,the liberation of formamidine from the hydrochloride and the synthesisof the enol ethyl ether.

The UBE-Takeda procedure for over seven steps (EP-A 055 108; EP-A 279556; DE-A 33 03 815; EP-A 124 780; EP-A 290 888; DE-A 32 22 519)includes in the first step the transformation of acrylonitrile tocyanoacetaldehyde-dimethylacetal. This step is very complex and requiresmajor investigations because the oxidation of acrylonitrile with methylnitrite leads to the formation of nitrous gases which have to bereoxidized to nitrite (EP-A 055 108).

The UBE-approach over 5 steps (DE-A 32 18 068, JP 58 065 262) needs twoequivalents of acetamidine hydrochloride. Acetamidine hydrochloride isexpensive; therefore it is disadvantageous to use two equivalents asstarting material.

The 5 step procedure from BASF (EP-A 172 515) uses o-chloroaniline forthe synthesis of the corresponding enamine. o-Chloroaniline is suspectedto provoke cancer. The enamine is used in the following step for thecyclization with acetamidine. After the formation of4-amino-5-aminomethyl-2-methylpyrimidine the o-chloroaniline has to beseparated and re-used in a complex process.

DE-A 34 31 270 describes the use of the same technology as EP-A 172 515,specifically using o-chloroaniline as amine, which is highlycarcinogenic and traces of o-chloroaniline have been found in theend-product vitamin B1.

Acrylonitrile reacts to aminopropionitrile (APN) in the presence ofammonia. APN is a commercially interesting intermediate, e.g. as it isuseful as starting material for both the synthesis of vitamin B₁ as wellas the synthesis of calcium pantothenate (see scheme 1).

The key-step in this approach is the cyclization of derivatives ofα-formyl-β-formylamino-propionitrile sodium salt with acetamidine. Thesederivatives can be for example the enamines, acetates ormethylenolethers of α-formyl-β-formylaminopropionitrile sodium salt (seefor example EP-A 001 760, DE-A 28 18 156, DE-A 23 23 845). For thecyclization reaction between a derivative ofα-formyl-β-formylaminopropionitrile sodium salt and acetamidine, theacetamidine has to be liberated from its hydrochloride. For thisprocedure commercially available acetamidine hydrochloride has to beneutralized with one equivalent of a base, usually sodium methanolate,leading to the unstable free acetamidine base and one equivalent of saltwaste. The synthesis of acetamidine hydrochloride is highly corrosiveand acetamidine itself is very expensive. Thus, severe drawbacks of thisprocedure are the formation of a salt, additional costs for the base andadditional reaction steps including work-up, e.g. by filtration of thesalts. The amine serves as a chemical auxiliary, upon reaction withacetamidine it is released and can be recycled, however, loss andcontamination of the end-product with the amine has been observed.

The patent application DE-A 35 11 273 describes the direct cyclizationof α-formyl-β-formylaminopropionitrile sodium salt with acetamidinehydrochloride with neither having to derivatize any of the mentionedstarting materials nor having to liberate the acetamidine from itshydrochloride:

The process consists of reacting α-formyl-β-formylaminopropionitrilesodium salt having a minimal purity of 92% with acetamidinehydrochloride in a solvent like isopropanol, methylisobutylcarbinol,open chain- or cyclic ethers during 4 to 6 hours at reflux yielding2-methyl-4-amino-5-formylaminomethylpyrimidine and subsequent hydrolysisleading to 4-amino-5-aminomethyl-2-methylpyrimidine. The reported yieldis 57%. Unfortunately it was not possible to obtain the reported yieldunder the reported conditions. The highest yield obtainable under thereported conditions was in fact 35%.

Main disadvantages of the process described in the DE-A 35 11 273 for anindustrial scale application are the poor yield—which makes the processeconomically unattractive—and the fact that the starting materials haveto have a minimal purity of 92%. In addition to that, only thehydrochloride of the acetamidine can be used.

J. Heterocyclic Chem. 1982, 19, 493-496 describes the synthesis of2-substituted 4-amino-6-methylpyrimidines by reacting e.g.propionitrile, benzonitrile or p-chlorobenzonitrile with3-aminocrotononitrile in the presence of tetramethylammonium hydroxidepenta-hydrate or potassium hydroxide.

It was therefore an object of the following invention to provide a newway to 4-amino-5-aminomethyl-2-alkylpyrimidine (compounds of formula V,especially 4-amino-5-aminomethyl-2-methylpyrimidine)

—which allows a considerable yield improvement and most preferredwithout using highly toxic reagents—like dimethylsulfate or o-chloroaniline.

Thus, the present invention is directed to a process for the manufactureof compounds of formula IV

wherein R¹ is an amino protecting group, and R² is hydrogen or C₁₋₁₀alkyl, comprisinga) reacting a compound of formula Ia, wherein M⁺ is a cation,

with an ammonium salt NH₄ ⁺X⁻, wherein X⁻ is an anion, in a solvent to acompound of formula II;

b) reacting a compound of formula II with a nitrile R²—CN (compound offormula III) in the presence of a base to a compound of formula IV.

R¹ is an amino protecting group. Such groups are known to the personskilled in the art. Examples of such a group are Boc(=tert-butoxycarbonyl), Cbz (=benzyloxycarbonyl), allyloxy, benzyl andCH₂C₆H₂(OMe)₃ (trimethoxyphenylmethylene), as well as amides (R¹═C(O)R⁴with R⁴ being hydrogen or straight- or branched-chain C₁₋₄ alkyl).Substituent R⁴ is preferably hydrogen, methyl, ethyl, n-propyl orn-butyl, more preferably R⁴ is hydrogen or methyl; most preferably R⁴ ishydrogen.

Preferably R¹ is formyl or acetyl, more preferably R¹ is formyl.

Concerning R²: the alkyl may be straight- or branched-chain or cyclic,preferably the C₁₋₁₀ alkyl is linear (C₁₋₁₀ alkyl) or branched (C₃₋₁₀alkyl). Preferably R² is methyl, ethyl, propyl, isopropyl or isoprenyl;preferably R² is methyl, isopropyl or isoprenyl, more preferably R² ismethyl.

The cation M⁺ is preferably selected from the group consisting of Li⁺,Na⁺, H⁺, ½ Mg²⁺ and ½ Zn²⁺.

The compound of formula Ia may be prepared by any method known to theperson skilled in the art, such as by the synthesis ofaminopropionitrile from the addition of ammonia to acrylonitrile,followed by formylation with methyl formate and sodium methoxide, asdescribed in EP-A 205 131 and DE-A 2323845.

The anion X⁻ is preferably selected from the group consisting ofchloride, bromide, sulfate, acetate, oxalate, HPO₄ ²⁻, more preferablyX⁻ is chloride, i.e. that ammonium chloride is reacted with a compoundof formula Ia to a compound of formula II.

Step a)

The solvent in which step a) may be performed is not critical. Suitablesolvents are e.g. alcohols such as methanol, 2-propanol and 1-butanol,aromatic hydrocarbons such as toluene, esters such as ethyl acetate,ethers such as diethyl ether and tetrahydrofuran, nitriles such asacetonitrile. The amount of the solvent is not critical either. Thereaction is in general carried out in a suspension of the enolate Ia inthe solvent, whereby the concentration of the starting enolate is in therange of from 10 to 50 weight-%, based on the total weight of thesuspension.

Preferably the nitrile R²—C≡N used in step b), e.g. acetonitrile, isused as solvent. For the preparation of vitamin B¹ it is preferred touse acetonitrile as solvent.

An example of a preferred mixture of solvents is a mixture of 2-propanoland toluene in a volume ratio of from 100:0 to 0:100, preferred in avolume ratio of from (80 to 50):(20 to 50), especially preferred in avolume ratio of from 65 to 35.

The temperature at which the reaction is performed should not exceed120° C., as the enolate starts to decompose above 120° C. If thedecomposition temperature of the enolate is lower, the reactiontemperature has to be decreased accordingly. The preferred temperatureis in the range of from 60 to 90° C., more preferably in the range offrom 70 to 85° C.

The reaction may be performed at atmospheric pressure, as well as undera pressure of 5 bar N₂ or under a pressure of 5 bar NH₃.

The molar ratio of the starting materials, i.e. the molar ratio of theammonium salt NH₄ ⁺X⁻ to the enolate of formula Ia may vary within arange of from 0.9:1 to 2.4:1. The best result was obtained with a molarratio of NH₄ ⁺X⁻ to the enolate Ia of 1.3:1.

The produced water does not have to be removed to achieve totalturnover.

The duration of the reaction is in the range of from 30 minutes to 20hours, preferably in the range of from 3 to 7 hours, depending on theamount of starting materials.

The starting materials can be added in any order to the reaction vessel.

According to the present invention it is advantageous to adjust thereaction conditions of step a) as follows:

-   -   a reaction temperature in the range of from 40 to 120 C,        preferred of from 60 to 90 C, more preferred of from 70 to 85 C    -   a pressure in the range of from 1 to 5 bar, preferred of from 1        to 2 bar;    -   a reaction time in the range of from 0.5 to 20 hours, preferred        of from 2 to 10 hours, more preferred of from 3 to 7 hours; most        preferred of from 3 to 5 hours;    -   under protective atmosphere.

Step b)

The compound of formula II may be successfully employed in purity in therange of from 75 to 99%.

If the compound of formula IV is used to synthesize Grewe diamineacetonitrile (i.e. R²=methyl) is used, in case of amproliumpropionitrile (i.e. R²=propyl) is used.

Advantageously the nitrile has already been used as solvent in step a).Thus, there is no need to remove the solvent, in which step a) has beenperformed, which means that after having performed step a) only a basehas to be added.

As base any base known to the person skilled in the art may be used. Ingeneral bases, where the corresponding acids have a pKa of >9 should besuitable. Examples of suitable bases are hydroxides such as alkali metalhydroxides (esp. potassium and/or sodium hydroxide) and pseudo-alkalimetal hydroxides, alkali metal hydrides like NaH and alcoholates such asodium methanolate and potassium tert-butanolate. The hydroxides may beused in solid form as well as an alcoholic solution. Aqueous solutionsof hydroxides may also be possible meaning that a certain amount ofwater is tolerated by the reaction system. Only a water content of ≧10weight-%, based on the total weight of the reaction system, has to beavoided.

If the nitrile also serves as solvent, it may be used in excess comparedto the compound of formula II. Otherwise it may be used instoichiometric amounts to the compound of formula II. Preferably thenitrile is used in at least 1.5 mol equivalents compared to the compoundof formula II.

The base may be used in catalytic amounts. Usually up to 1 equivalent(preferably from 0.01-1 equivalent) compared to the compound of formulaII are used. Preferably ca. 0.2 mol %, based on the amount of thecompound II are used.

Step b) may be performed at a temperature in the range of from 30 to120° C., more preferably step b) may be performed at a temperature inthe range of from 35 to 60° C., even more preferably step b) may beperformed at a temperature in the range of from 40 to 50° C., mostpreferably step b) may be performed at a temperature in the range offrom 40 to 45° C. (optimal temperature: 42° C.).

The starting materials can be added in any order to the reaction vessel.

According to the present invention it is advantageous to adjust thereaction conditions of step b) as follows:

-   -   a reaction temperature in the range of from 10 to 120 C,        preferred of from 20 to 85 C, more preferred of from 40 to 45 C    -   a pressure in the range of from 0.5 to 5 bar, preferred of from        1 to 3 bar;    -   a reaction time in the range of from 0.5 to 20 hours, preferred        of from 2 to 18 hours, more preferred of from 7 to 15 hours;    -   under protective atmosphere.

The compounds of formula II, especially wherein R¹ is formyl, acetyl ortert-butoxy-carbonyl, are novel and have not been characterized untilnow. Preferred are the compounds of formula II, wherein R¹ is formyl andacetyl, more preferred is the compound of formula II, wherein R¹ isformyl.

Thus, the present invention is directed totrans-N-(3-amino-2-cyanoallyl)formamide, tocis-N-(3-amino-2-cyanoallyl)formamide and any mixture thereof, as wellas to trans-N-(3-amino-2-cyanoallyl)acetamide, tocis-N-(3-amino-2-cyanoallyl)acetamide and any mixture thereof, and alsoto the compounds of formulae IIa(trans-1-N(tert-butoxycarbonyl)-3-amino-2-cyanoallylamin), IIb(cis-1-N(tert-butoxycarbonyl)-3-amino-2-cyanoallylamin) and IIc (anymixture of compounds of formulae IIa and IIb).

Since the compounds of formula II (especially with R¹=formyl, acetyl ortert-butoxy-carbonyl) are novel, a process for their preparation is alsonovel. Thus, the present invention is also directed to a process for themanufacture of compounds of formula II

wherein R¹ is an amino protecting group (as defined and with thepreferences as given above), comprising the step of reacting a compoundof formula Ia, wherein M⁺ is a cation (as defined and with thepreferences as given above)

with an ammonium salt NH₄ ⁺X⁻, wherein X⁻ is an anion (as defined andwith the preferences as given above) in a solvent (as defined and withthe preferences as given above) to a compound of formula II.

The preferences and preferred conditions for this reaction have alreadybeen disclosed above.

Another embodiment of the present invention is the use of a compound offormula IVa,

wherein R¹ is an amino protecting group, and R² is methyl, preferablyobtained according to a process of the present invention, asintermediate in a process for the preparation of vitamin B₁.

A further object of the present invention is the use of a compound offormula II,

wherein R¹ is an amino protecting group (as defined and with thepreferences as given above), preferably obtained according to a processof the present invention, as intermediate in a process for thepreparation of vitamin B₁.

Moreover, an embodiment of the present invention is a process for themanufacture of Grewe diamine (GDA;5-aminomethyl-2-methyl-pyrimidine-4-yl-amine), wherein from a compoundof formula IVa the amino protecting group R¹ is removed.

The present invention encompasses also a process for the manufacture ofGrewe diamine, wherein a compound of formula IV, wherein R¹=formyl oracetyl; and R²=methyl, is hydrolysed. The hydrolysis may be carried outin the presence of bases such as hydroxides and ion exchangers as e.g.described in WO 2007/104 442; WO 2006/079 504 and DE-A 35 11 273.

The thus obtained GDA may, e.g., be further reacted with carbondisulfide and 3-chloro-5-acetoxypentan-2-one or another chloroketonederivate such as 3-chloro-5-hydroxypentan-2-one,3-mercapto-5-hydroxypentan-2-one or 3-mercapto-5-acetoxypentan-2-one orany mixture thereof to form the compound of formula VI

with R³ being C₁₋₄-alkanoyl, preferably acetyl (see e.g. G. Moine andH-P. Hohmann in Ullmann's Encyclopedia of Industrial Chemistry, VCH,Vol. A 27, 1996, 515-517 and the references cited therein).

Therefore, such a process for the manufacture of a compound of theformula VI is also a part of the present invention.

The compound of formula VI may then further be reacted with an acid toform the compound of formula VII

(see e.g. G. Moine and H-P. Hohmann in Ullmann's Encyclopedia ofIndustrial Chemistry, VCH, Vol. A 27, 1996, 515-517 and the referencescited therein).

Therefore, such a process for the manufacture of a compound of formulaVII is also a part of the present invention.

The compound of the formula VII may then further be oxidized, preferablywith H₂O₂, to vitamin B₁ of formula VIII

(see e.g. G. Moine and H-P. Hohmann in Ullmann's Encyclopedia ofIndustrial Chemistry, VCH, Vol. A 27, 1996, 515-517 and the referencescited therein).

Therefore, the present invention comprises a process for the manufactureof vitamin B₁ wherein from a compound of formula IVa

the amino protecting group R¹ is removed to obtain Grewe diamine, thethus obtained Grewe diamine is further reacted to a compound of formulaVII,

preferably as described above in more detail, and the thus obtainedcompound of formula VII is further oxidized, preferably with H₂O₂, toyield vitamin B1.

Preferably R¹ in formula IV is C(O)R⁴ with R⁴ being hydrogen orstraight- or branched-chain C₁₋₄ alkyl (compound of formula IVa),

so that the group C(O)R⁴ is hydrolysed to obtain Grewe diamine asdescribed e.g. in the references cited above.

The overall reaction scheme starting with a compound of formula I tovitamin B1 is shown in FIG. 1.

The present invention comprises also the use of a compound of formulaIVa obtained according to the process of the present invention asdescribed above as intermediate in a process for the manufacture ofvitamin B1.

Finally the present invention comprises the use of GDA obtained asdescribed above as intermediate in a process for the manufacture ofvitamin B1.

The invention will now be illustrated in the following non-limitingexamples.

EXAMPLES Example 1 Preparation of the enamine fromα-formyl-β-formylaminopropionitrile sodium salt

Equipment: 1000 ml Two-necked round bottom flask, Argon supply,mechanical stirrer, oil heating bath

100.0 g of α-formyl-β-formylaminopropionitrile sodium salt (88% purity)and 37.3 g of ammoniumchloride were suspended in 500 ml of a mixture ofisopropanol: toluene (65:35 Vol %) and heated to 130° C. bathtemperature. The mixture was refluxed for 3 hours while stirring slowly(50 revolutions per minute). The mixture was allowed to cool to 25° C.after the three hours. The suspension was filtrated over a P3 Glassfilter and washed with MeOH. The solvent was evaporated under reducedpressure (40° C. bath temperature, 50 mbar). A yellowish viscoseous oilwas obtained. Yield: Filtrate 71.52 g (purity 75.6%): 75%.

Purification

30 g of the crude product were purified over 400 g SiO₂. The substancewas therefore absorbed on hydromatrix with 7 L of a mixture of methanol(MeOH): methylenechloride (CH₂Cl₂) (1:9; Vol %) and a flow of 150 mL/minat 13 bar. In the end 20 g of product (purity of 90%) were obtained.

Spectroscopic Characterization:

¹H-NMR, DMSO-d6, δ in ppm: Z isomer δ=3.65 (d, J=5.65 Hz, 2H, CH₂); 6.45(d, ³J=11.11 Hz, 2H, NH₂); 6.86 (t, ³J=11.11 Hz, 1H, C═CH); 7.98 (d,J=1.69 Hz, 1H, HCO), 8.15 (m, 1H, NH). E isomer: δ=3.72 (d, J=6.03 Hz,2H, CH₂); 6.62 (d, J=10.7 Hz, 2H, NH₂), 6.94 (t, J=10.7, 1H, C═CH), 8.03(d, J=1.69 Hz, 1H, HCO), 8.35 (m, 1H, NH).

¹³C-NMR, DMSO-d6, δ in ppm: E isomer: δ=32.9, 73.8, 123.5, 148.9, 161.4.

Z isomer: 37.6, 71.8, 119.9, 150.8, 160.8.

MS (Electron Impact): M⁺ 269 (bis-trimethylsilane adduct).

Examples 2-8

Example 1 was repeated applying the same protocol, but the solvent andthe reaction time were different. The reaction temperature was thereflux-temperature of the corresponding solvent.

Reaction Time Yield Purity Example Solvent [hours] [%] [%] 2 Methanol 775 71 3 Toluol 7 68 65 4 Isopropanol 7 78 65 5 1-Butanol 3 60 49 6Acetonitrile 3 46 42

Example 1 was repeated applying the same protocol, but the amount ofNH₄Cl was changed.

mol % Yield Purity Example NH₄Cl [%] [%] 7 1 67 72 8 2.4 71 62

Example 9 Reaction of N-(3-amino-2-cyanoallyl)formamide withacetonitrile to N-formyl Grewe Diamine

Equipment:

20 mL two-necked flask, fitted with a magnetic stirrer, a thermometer, areflux condenser, and an argon supply.

Preparation:

250 mg of N-(3-amino-2-cyanoallyl)formamide were dissolved in 7.5 mL ofacetonitrile and 74.8 mg of tetramethyl ammonium hydroxide pentahydratewere added. The solution was stirred for 16 hours at 42° C. Then thesolvent was evaporated. The yield of N-formyl Grewe diamine was 58%based on converted enamine (80% conversion).

Example 9 was repeated applying the same protocol, but the temperaturewas changed.

Yield Example Temperature [%] 10 120° C. 29 11  82° C. 27.4 12  40° C.58

Example 9 was repeated applying the same protocol, but the temperatureand the base was changed.

Amount Yield Example Base [mol %] Temperature [%] 13 NaOCH₃ 0.2 82° C.13.8 14 (CH₃)₃COK 0.2 82° C. 20 15 KOH 0.2 82° C. 15

1. trans-Isomer of a compound of formula II with R being an aminoprotecting group, preferably with R being formyl, acetyl ortert-butoxycarbonyl.


2. cis-Isomer of a compound of formula II with R being an aminoprotecting group, preferably with R being formyl, acetyl ortert-butoxycarbonyl.


3. A mixture of cis- and trans-isomers according to claim
 1.


4. A process for the manufacture of compounds of formula II

wherein R¹ is an amino protecting group, comprising the step of reactinga compound of formula Ia, wherein M⁺ is a cation

with an ammonium salt NH₄ ⁺X⁻, wherein X⁻ is an anion in a solvent to acompound of formula II.
 5. A process for the manufacture of compounds offormula IV

wherein R¹ is an amino protecting group, and R² is hydrogen or C₁₋₁₀alkyl, comprising a) reacting a compound of formula Ia, wherein M⁺ is acation,

with an ammonium salt NH₄ ⁺X⁻, wherein X⁻ is an anion, in a solvent to acompound of formula II

b) reacting a compound of formula II with a nitrile R²—CN in thepresence of a base to a compound of formula IV.
 6. The process accordingto claim 4, wherein R¹ is formyl or acetyl; preferably wherein R¹ isformyl.
 7. The process according to claim 5, wherein R² is methyl,ethyl, propyl, isopropyl or isoprenyl; preferably R² is methyl,iso-propyl or iso-prenyl, more preferably R² is methyl.
 8. A process forthe manufacture of Grewe diamine, wherein from a compound of formula IVthe amino protecting group R¹ is removed.
 9. A process for themanufacture of Grewe diamine, wherein a compound of formula IV, whereinR¹=formyl or acetyl; and R²=methyl, is hydrolysed.
 10. A process for themanufacture of a compound of formula VI

wherein R³ is C₁₋₄-alkanoyl, preferably acetyl, characterized in thatGrewe diamine, preferably obtained by a process according to claim 8, isreacted with carbon disulfide and a chloroketone derivative, preferablyselected from the group consisting of 3-chloro-5-hydroxypentan-2-one,3-chloro-5-acetoxypentan-2-one, 3-mercapto-5-hydroxypentan-2-one,3-mercapto-5-acetoxypentan-2-one and any mixture thereof, to a compoundof formula VI.
 11. A process for the manufacture of a compound offormula VII

characterized in that a compound of formula VI, preferably obtained in aprocess according to claim 10, is further reacted with an acid to acompound of formula VII.
 12. A process for the manufacture of vitaminB₁, characterized in that from a compound of formula IVa

the amino protecting group R¹ is removed to obtain Grewe diamine, thethus obtained Grewe diamine is further reacted to a compound of formulaVII,

preferably as claimed in claim 11, and the thus obtained compound offormula VII is further oxidized, preferably with H₂O₂, to Vitamin B₁.13. The process according to claim 12, wherein R¹ is C(O)R⁴ with R⁴being hydrogen or straight- or branched-chain C₁₋₄ alkyl (compound offormula IVa), and the group C(O)R⁴ is hydrolysed to obtain Grewediamine.


14. Use of Grewe diamine obtained according to a process as claimed inclaim 8 as intermediate in a process for the preparation of vitamin B₁.15. Use of a compound of formula IVa,

wherein R¹ is an amino protecting group, obtained according to a processas claimed in claim 5, as intermediate in a process for the preparationof vitamin B₁.
 16. Use of a compound of formula II,

wherein R¹ is an amino protecting group, obtained according to a processas claimed in claim 4, as intermediate in a process for the preparationof vitamin B₁.